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Electric Circuits
The capacitance of a certain variable capacitor may be varied between limits of 1 x 10^(-10) F and 5 x 10^(-10) F by turning a knob attached to the movable plates. The capacitor is set to 5 x 10^(-10) F, and is charged by connecting it to a battery of EMF 200V.
(i) What is the charge on the plates?The battery is then disconnected and the capacitance changed to 1 x 10^(-10) F.
(ii) Assuming that no charge is lost from the plates, what is now the PD between them?
(iii) How much mechanical work is done against electrical forces in changing the capacitance?
(i) What is the charge on the plates?The battery is then disconnected and the capacitance changed to 1 x 10^(-10) F.
(ii) Assuming that no charge is lost from the plates, what is now the PD between them?
(iii) How much mechanical work is done against electrical forces in changing the capacitance?
Electric Circuits
The capacitance of a certain variable capacitor may be varied between limits of 1 x 10^(-10) F and 5 x 10^(-10) F by turning a knob attached to the movable plates. The capacitor is set to 5 x 10^(-10) F, and is charged by connecting it to a battery of EMF 200V.
(i) What is the charge on the plates?The battery is then disconnected and the capacitance changed to 1 x 10^(-10) F.
(ii) Assuming that no charge is lost from the plates, what is now the potential difference between them?
(i) What is the charge on the plates?The battery is then disconnected and the capacitance changed to 1 x 10^(-10) F.
(ii) Assuming that no charge is lost from the plates, what is now the potential difference between them?
Electric Circuits
Derive an expression for the electrical energy stored in a capacitor of capacitance C when charged to a potential difference V
If C = 2uF and V = 4V, calculate:
(i) the final energy stored in the capacitor (ii) the work done by the battery in the charging process. Hence account for any difference between your answers above.
If C = 2uF and V = 4V, calculate:
(i) the final energy stored in the capacitor (ii) the work done by the battery in the charging process. Hence account for any difference between your answers above.
Electric Circuits
A capacitor is charged through a resistor using a battery of constant EMF.
(i) Draw sketch graphs on the same time axis showing how the charge on the capacitor and how the current through the circuit vary with time. Qualitatively explain their shapes.
(i) Draw sketch graphs on the same time axis showing how the charge on the capacitor and how the current through the circuit vary with time. Qualitatively explain their shapes.
Electric Circuits
A horizontal portion of a circuit contains 3 aligned points A, B and C. A 2.0uF and a 3.0uF capacitor are shunted between A and B, and there is a 5uF capacitor between B and C. Above this alignment is a series connection of a 100V battery and a switch S1 connected to A and C. Below the alignment is a 10 ohm resistor and a switch S2 connected to A and C. The switches are initially opened.
(i) Draw a diagram of the circuit
(ii) If a resistor is connected in series to the 10 ohm resistor, will the flow of charge be affected? Explain.
(i) Draw a diagram of the circuit
(ii) If a resistor is connected in series to the 10 ohm resistor, will the flow of charge be affected? Explain.
Electric Circuits
A horizontal portion of a circuit contains 3 aligned points A, B and C. A 2.0uF and a 3.0uF capacitor are shunted between A and B, and there is a 5uF capacitor between B and C. Above this alignment is a series connection of a 100V battery and a switch S1 connected to A and C. Below the alignment is a 10 ohm resistor and a switch S2 connected to A and C. The switches are initially opened.
(i) Draw a diagram of the circuit
(ii) If S1 is opened and S2 closed, how much charge flows through the 10 ohm resistor?
(iii) If another resistor is connected in series to the 10 ohm resistor, will the flow of charge be affected? Explain.
(i) Draw a diagram of the circuit
(ii) If S1 is opened and S2 closed, how much charge flows through the 10 ohm resistor?
(iii) If another resistor is connected in series to the 10 ohm resistor, will the flow of charge be affected? Explain.
Electric Circuits
A horizontal portion of a circuit contains 3 aligned points A, B and C. A 2.0uF and a 3.0uF capacitor are shunted between A and B, and there is a 5uF capacitor between B and C. Above this alignment is a series connection of a 100V battery and a switch S1 connected to A and C. Below the alignment is a 10 ohm resistor and a switch S2 connected to A and C. The switches are initially opened.
(i) Draw a diagram of the circuit
(ii) Calculate the time constant and tge half-life of the circuit and state the significance of each value.
(i) Draw a diagram of the circuit
(ii) Calculate the time constant and tge half-life of the circuit and state the significance of each value.
Electric Circuits
A horizontal portion of a circuit contains 3 aligned points A, B and C. A 2.0uF and a 3.0uF capacitor are shunted between A and B, and there is a 5uF capacitor between B and C. Above this alignment is a series connection of a 100V battery and a switch S1 connected to A and C. Below the alignment is a 10 ohm resistor and a switch S2 connected to A and C. The switches are initially opened.
(i) Draw a diagram of the circuit
(ii) If S2 is left open and S1 closed, calculate the quantity of charge on each capacitor. How much energy does each store?
(i) Draw a diagram of the circuit
(ii) If S2 is left open and S1 closed, calculate the quantity of charge on each capacitor. How much energy does each store?
Electric Circuits
What limits the quantity of charge a capacitor can store?
Electric Circuits
A charged capacitor of capacitance C can be discharged through a resistor R. At time t after the discharge has started, the charge Q remaining on the capacitor can be given by the expression:
Q = Qoe^(-t/RC)
(i) Use this equation to obtain an expression for the half-life T1/2 of the discharge process.
(ii) Use this equation to define the time constant t of the discharge
(iii) Compare the values of T1/2 and t.
Q = Qoe^(-t/RC)
(i) Use this equation to obtain an expression for the half-life T1/2 of the discharge process.
(ii) Use this equation to define the time constant t of the discharge
(iii) Compare the values of T1/2 and t.
